Brucellosis is among the most widespread zoonotic infections causing human suffering and economic losses in livestock [1–3]. However, it is often a neglected cause of morbidity in many regions of the world [3, 4]. The disease is most common in rural areas among those involved in animal husbandry, meat-packers, dairy workers, veterinarians, consumers of unprocessed dairy products and in urban livestock keeping populations [2, 5]. Brucella infection is transmitted from animals (cattle, goats, pigs, sheep, camels and buffaloes) to humans by bacteria belonging to the genus Brucella. B. abortus, B. suis, and B. melitensis are the causative agents, which affect cattle, swine, goats and sheep respectively are most pathogenic to humans . B. canis and marine species also have zoonotic potential but are not as pathogenic.
The global burden of human brucellosis remains enormous with more than 500,000 infections per year worldwide [4–6]. Brucellosis has been reported in the Middle East , Mediterranean region , Northern and Sub-Saharan countries in Africa [4, 6, 8] with prevalence of 5-55% in humans and 8-46% in animals . For example, in central Greece, prevalence was 32.49 cases/100,000 inhabitants . In Iran, a Brucellosis endemic country, a study on brucellosis and HIV co-infection found a very high prevalence of 73% among HIV positive patients compared to 24% in HIV negative patients indicating a statistical difference in infection rates . Among hospital patients in Markudi Nigeria, overall brucellosis prevalence was 7.6%, and 43.8% of these were abattoir workers and butchers . Over 55% of 7161 people examined in different parts of Western Nigeria have positive Brucella abortus antibodies in their sera. Higher incidences of titres were found among dairy farmers and slaughter men than in the general population. The rates of infection among human and cattle populations in two farms studied were very similar . In Egypt, incidence ranges from 0.28 to 70 per 100,000 population [4, 11] and 11% prevalence among hospital patients .
Brucellosis is a highly prevalent disease in Uganda with 7 – 42.2% [2, 13, 14] among cattle and goats, posing a big threat to abattoir workers and consumers. A study done among hospital patients estimated 18-24% brucellosis prevalence  while it was estimated at 6 – 7% among herdsmen and consumers of raw milk and products . In Kampala, Uganda, of 150 patients with joint pain, general malaise, and/or constant headache, 73% were found to be suffering from malaria and 13.3% from brucellosis showing a scenario often leading to misdiagnosis .
Few recent studies in Africa and globally have considered the abattoir workers as an occupational high risk group. A study among high risk groups in Erzurum, Turkey found higher infection among abattoir workers . In India, assessment of 165 serum samples of abattoir associated personnel with dot-ELISA found 25.5%, 40% and 11% positive for brucellosis, listeriosis and tuberculosis respectively . In Pakistan, Mukhtar and Kokab found 21.7% prevalence using ELISA with job category, age and duration in the abattoir as significant risk factors .
Diagnosis of brucellosis based on the clinical picture alone is difficult due to similarity with clinical presentations of other infections [3, 9]. Symptoms and signs are non-specific and several other febrile illnesses, for example glandular fever, influenza, malaria and enteric infections may be simulated [11, 18, 19]. When an unusual complication is present, it may be overlooked . Therefore, laboratory testing is an absolute prerequisite for proper diagnosis through blood culture and isolation of the causative organisms or serological testing . However, culture requires special media, takes several weeks of incubation and has low sensitivity. Serological tests including the serum agglutination test (SAT or STAT), anti-human globulin test (Coombs test), complement fixation test (CFT) and Enzyme-linked Immunosorbent Assay (ELISA), therefore, are indispensable for an accurate diagnosis .
Malaria is endemic in Uganda with prevalence as high as 70% in patients with pyrexia of unknown origin . Few studies have focused on brucellosis prevalence in Africa [4, 6] and misdiagnosis with common conditions such as malaria and typhoid remains a challenge. In Uganda, brucellosis prevalence and the occupation link is unknown to health workers, and malaria, a common tropical disease which sometimes clinically mimics brucellosis has not been widely studied in apparently healthy populations [12, 16]. There is no published data on prevalence of brucellosis in Uganda among abattoir workers which is a high risk group and the study therefore sought to address this gap. At the same time, this study assessed the prevalence of malaria in this apparently healthy population.